The "bar-mode" property determines the way LevelBar interprets the
value properties to draw the level fill area. Specifically, when the value is
LevelBarModeContinous, LevelBar will draw a single block
representing the current value in that area; when the value is
LevelBarModeDiscrete, the widget will draw a succession of separate
blocks filling the draw area, with the number of blocks being equal to the
units separating the integral roundings of "min-value" and "max-value".